1. Briefly describe the excretory, skeletal,
muscle and nervous systems and method of feeding of the supposed immediate
ancestor of the first vertebrate, and relate each of these characteristics
to its function in the evolution of fish.
2. Relate fish evolution to the geologic time
in which it occurred, including the names and appearance of the oldest fossil
fish.
3. Create a fish family tree showing the relationship
of the Ostracoderms, Cyclostomata, Placoderms, Chondrichthyes and Osteichthyes.
4. Similarly to objective #4, draw a family
tree of the Osteichthyes showing the relationship between the lobefins and
the ray fins; describe any outstanding features of each group.
5. Describe the basic differences between pronephros,
mesonephros and metanephros kidneys, and relate eaach type to the vertebrate
group in which it is found.
6. Describe the external appearance of lampreys
and hagfish.
7. Outline the life cycle of the sea lamprey,
including the apparent trigger for metamorphosis.
8. List the ways in which the Chondrichthyes
are more advanced than the cyclostomes.
9. Describe the heterocercal tail of the shark.
Describe in detail how the body plan of the shark helps it achieve lift.
10. Describe the respiratory apparatus of the
shark and special problems it encounters because it lacks an operculum.
11. Compare the most common reproductive patterns
in sharks and in bony fish.
12. State the original function of the swim
bladder, and describe the extent to which it is still used for that function
in the different osteichthyes.
13. Describe the anatomy and function of the
lateral line system, and name the fish groups which have this organ.
14. Compare and contrast the homocercal tail
of the bony fish with the heterocercal tail of the sharks.
15. Describe the differences between ram ventilation,
the usage of spiracles and the countercurrent mechanism employed by fish
to accomplish respiration.
16. Name the fish groups in which the notochord
is completely replaced by vertebrae.
17. Name and describe the characteristics of
the two main body patterns in the teleosts, and give examples of local fish
representing each body pattern.
18. List and briefly describe the ways in which
the bony fish are more advanced than the shark group and cyclostomes.
19. Define catadromous and anadromous and give
examples organisms described by these terms.
Resources: Text: Animal Diversity, Chapter
16
Internet Resources:
http://www.ucmp.berkeley.edu/vertebrates/basalfish/chondrintro.html
http://www.biology.ualberta.ca/jackson.hp/iwr/taxa/Chondrichthyes.html
http://www.seaworld.org/Fishes/class.html
http://www.mhhe.com/hickmanad4e
FISH: CLASS CHONDRICHTHYES, CLASS OSTEICHTHYES
-16th century included seals, whales, amphibians,
crocodiles and hippos;
jellyfish, starfish etc
**Today: gill breathing, ectothermic,
aquatic vertebrates that posses fins and
have skin usually covered w/scales;
masters of aquatic environment
-humans likely to be uninformed about fishes:
1. environment alien to humans
2. most nature shows and books devote
time and space to birds/mammals
-~23,000 species, more than all other vertebrates put together
Evolution- may have arisen from
free swimming larval tunicate
Neotony- ability of a larval
form to reproduce, larval tadpole form will escape adult
sessile form
CLASSIFICATION- ** not even a majority of ichtyologists agree on plan
Subphylum Vertebrata
Superclass Agnatha (no jaw)-
hagfish/lamprey
Superclass Gnathostomata (jawed fishes)
Class Chondrichthyes-
skeleton of cartilage
-no operculum
(gill cover); no swim bladder
-sharks, skates,
rays
Class Osteichthyes-
bony skeleton (teleostomi)
-have operculum,
swim bladder
Subclass
Actinopterygii- ray finned fish
CHARACTERISTICS:
Superclass Agnatha
-eel-like
-no paired appendages
-notochord persists
-biting mouth; predatory/parasitic existance
-cartilagenous cranium
-simple heart; one atrium, one auricle,
aortic arches in gill region
-dorsal nerve cord
-16 pairs of gills in hagfish; 7 pr in lampreys
-digestive system w/o stomach; spiral
valve separates posterior end of esophagus
from straight intestine; typhlosole
partitions intestine in spiral manner to increase
surface area
-fertilization external; hagfish hermaphroditic
(rare in vertebrates) but only one gonad
functional; lampreys dioecious w/larva
and metamorphosis
-kidneys- in vertebrates differ in relationship
to blood system, complexity and efficiency
(maintain same mineral levels inside
as those present outside)
Pronephric- most primitive,
in embryonic stages of all vertebrates, functional in adults
of none
Mesonephric- fish and amphibians
Metanephric- reptiles, birds,
mammals
Lamprey life cycle
-feed as adults in open ocean, near end
of life migrate to freshwater streams to mate
-male begins nest building and then joined
by female
-female attaches to stone w/mouth to maintain
position over nest, male attaches to
dorsal side of female head
-egg and sperm shed into nest
-eggs stick to pebbles and become covered
by sand
-eggs hatch into ammocoetes larva; ~2
weeks burrow into sand or mud; live as filter
feeders
-metamorphosis can last 3-7 years!!
at time of metamorphosis endostyle becomes a
thyroid gland and chemical stimulation
by thyroxin triggers metamorphosis
Class Chondrichthyes
-sharks, skates, rays ~760 species
-predaceous/carnivorous, scavengers
-biting mouth parts located ventral,
paired appendages
-cartilaginous skeleton
-no swim bladder; sharks heavier than
water, therefore, must remain in motion to avoid
sinking
Heterocercal tail w/vertebrae
in dorsal lobe gives lift; streamlining w/flat ventral
surface can also aid lift
-no operculum (gill cover), 7 pr exposed gills
-tough skin w/ placoid scales. Toothlike
structures w/ dentin coverings; scales project
toward posterior to give sandpaper texture
(posterior projections reduces friction)
-teeth modified placoid scales. Row
of teeth on outer edge of jaw backed up by rows
of teeth attached to a ligamentous
band. As outside teeth wear down or break they
are replaced by newer teeth
-dioecious; internal fertilization; oviparous, ovoviviparous and viviparous (?)
-secondary facilities: smell, lateral line system; bioelectric sense
-largest fish- whale shark, longer than
10m, not predatory; filter feeder
-most feared; great white (Jaws)
27 of 760 species known to attack man
(often terretorial confrontation or provocation)
Class Osteichthyes- bony fish
-skeleton (at least partly) made of ossified
bone
-swim bladder for bouyancy; gill
w/ operculum
-body form great example of adaptive radiation
(*one form generating many variations
dependent upon niche)
-skin w/ scales: ganoid- tile
like, diamond shape, little overlap
cycloid
- smooth, light, thin, flexible, overlap
ctenoid
- rough, light, thin, flexible, overlap
or none ---> catfish
-terminal mouth
-dioecious, external fertilization;
oviparous
-Super order Teleostei ~ 21,800 species,
represent 96% of all fish
-homocercal tail- upper and lower
lobes nearly equal in size
-lungs of primitive groups (lung fish)
evolved into swim bladder
-scale growth discloses seasonal changes
in growth rate, much like trees; scale growth
proportional to increase in length
GENERAL ADVANCES:
1. locomotion
-design to overcome resistance encountered
in dense water
-less energy expenditure for a fish to
swim than a terrestrial animal to run
-friction reduced between fish and water
by streamlined shape and mucus secretions
that lubricate body surface
-bouyancy properties of water also contribute
to efficiency; fish spend little energy
combatting the pull of gravity
-fishes move using fins and body wall to
push against water
-body wall muscles arranged in bundles called myotomes
-anyone who has eaten fish recognize
muscle layers that are arranged in a
muscles extend posteriorly
and anteriorly in zig zag fashion, contraction of
myotome effects large portion
of body wall.
-myotomes on opposite sides of body contract
alternately; vertebral column prevents
body from collapsing; body flexes laterally.
Waves of contraction pass along body
from anterior ---> posterior
*lampreys, hagfish and eels swim inefficiently
at best; use of fin minimal
*tuna, mackral- very efficient, fast; supplement
w/ caudal fin that is tall and forked
(forked shape reduces surface area
that could cause turbulance)
*backward swimming possible using pectoral
and pelvic fins and reversal of muscular
waves, little used and poorly executed
GAS EXCHANGE
-environment of fish contains 2.5% of the
oxygen in air, therefore, large quantities of water
must pass over gill
-muscles around pharynx and opercular
cavity power pump that moves water into mouth
and over gill
*operculum closed/ mouth open --->
water drawn into pharynx, hydrostatic pressure
draws water across gills
*mouth closed/ operculum opens ---> water out
-Sharks, open ocean bony fish maintain
water flow by holding mouth open while swimming,
RAM VENTILATION
-spiracles (sharks) are modified
gill slits behind eye; used as an alternate route for water
entering pharynx
-Exchange very efficient; exchange at
gill lamellae
Counter current mechanism-
water and blood move in opposite directions on either
side of lamellae
-ensures the amount of oxygen
is water always greater than oxygen in blood,
therefore, always maintains
diffusion gradient
BLOOD OXYGEN %
WATER OXYGEN %
Parallel system
BLOOD OXYGEN %
WATER OXYGEN %
Bouyancy- fish maintain verticle position in water in 4 ways:
1. incorporate low density compounds
into tissues; fish (especially livers) are
saturated w/ bouyant
oils.
2. use fins to provide lift (caudal fin of shark)
3. reduce heavy tissue- shark cartilage; fish bone less dense than terrestrial animals
4. swim bladder- regulate volume
of gas; gas secreted into bladder from blood;
some get air directly
into bladder through pneumatic ducts from esophagus.
NERVOUS AND SENSORY FUNCTIONS
-CNS of brain and spinal cord, sensory
receptors all over body
Receptors for touch, temp., vision,
olfaction, balance, water movement
Salmon/lampreys rely heavily on smell to return home
-eyes similar to other vertebrates, most
lidless, focus by moving lens up or back in eye
(most other vertebrates change shape
of lens)
-lateral line system- sensory
pits in epidermis of skin connecting canals running
below epidermis; receptors stimulated
by water moving against them; used to
detect prey or predator; low frequency
sound may also be detected (vibrations)
-Electroreception- detection of
electric fields; demonstrated in over 500 species of
fish in seven families of Chondrichthyes
and osteichthyes
*used to detect prey or to orient
toward or away from objects; best known in sharks
and rays
REPRODUCTION AND DEVELOPMENT
-millions of eggs produced in a single season
-numbers reflect hazards of developing in
aquatic habitats unattended by parent:
Vast majority will not survive to reproduce
-many eggs never get fertilized
-fertilized eggs may wash ashore and dry
-many eggs and embryo may be smashed by currents or tides
-predation
*if only four of the millions survive the pop. will double
-large #s not only strategy: mating
behavior, nesting behavior, help protect against
predation, sedimentation, fouling
-mating can occur in schools (spawning pheromone)
-vast majority of fish are oviparous
(w/ external fertilization) Exceptions: guppies,
some sharks ovoviviparous
grey sharks, hammerheads are
viviparous (modified oviducts diverts nutrients
from female to yolk sac of developing
embryo)
*sharks fertilize internally
-male sharks have modified pelvic fin,
clasper; during copulation a clasper is inserted
into cloaca of female; sperm travel
along groove on clasper. Result in higher
proportion of eggs being fertilized,
therefore, fewer eggs
-few cases of shortterm parental care
after birth but for most part they are on their own
Sticklebacks; sunfish
-growth temperature dependent
Temperate regions ---> rapid
growth in summer, little in winter reflected in scales
-migratory fish
Catadromous- most of life
in FW, spawn in salt water (eel)
Anadromous- most of life in salt water, spawn in FW (salmon)
*guided by odors, imprinted when
migration to sea begins. Create maps of odors as
guide upon return